1. Field of the Invention
The present invention relates to a linear motion guide unit adapted for use in various types of machinery such as diverse industrial robots, semiconductor manufacturing machines, machine tools, and so on.
2. Description of the Prior Art
Most linear motion guide units used extensively in diverse fields of machinery such as various industrial robots, semiconductor manufacturing apparatus, precision machines, machine tools, and so on are in general comprised of a track rail and a slider, which fits over and conforms to the track rail for sliding movement. The slider is chiefly composed of a carriage and end caps. In most sliders ever used, the carriage is usually jointed together with the end caps by tightening machine screws and so on. Among the more recent advances in sliders, on the other hand, is known a slider in which the components: carriage and end caps are joined together in a fitting relation with no use of any fastener.
A linear motion guide arrangement is disclosed in, for example Japanese Patent No. 2936116, in which the snap connection means are used to secure the carriage member and the reversing bodies to the guide carriage housing. Thus, there is disclosed a construction in which no fixing screw is used for jointing together components and parts. In detail, the reversing bodies are secured to the fore-and-aft ends of the carriage, one to each end, with the projections of the reversing bodies coming into engagement with the grooves on the upper side of the carriage. The combination of the carriage and reversing bodies is accommodated in the guide carriage housing with the fore-and-aft outside end faces being covered with the guide carriage housing and held in position by the snap connection means. With the linear motion guide arrangement recited earlier, moreover, there is provided a recirculating-ball circuit including a return guide raceway formed in the carriage and curved ball guides formed in the reversing bodies, one to each body. Engagement of the grooves on the upper side of the carriage with the projections of the reversing bodies serves to bring the curved ball guides into alignment with the return guide raceway, thereby establishing the recirculating-ball circuit. In addition, the sealing plates are applied to the end surfaces of the end plates of the guide carriage housing and locked by snapping any locking nose of the sealing plates into the associated locking recess in the end plates of the guide carriage housing.
Disclosed in Japanese Utility Model Laid-Open No. 133122/1986 is a linear guide means in which a slider body has mounted on fore-and-aft ends thereof with end caps, one to each end, and the resulting combination fits in a carriage housing with being encircled with the housing. Then, bolts are screwed to unite together all the slider body, end caps and housing. In the prior linear guide means recited just above, the turnarounds and the return passages provided for the recirculating-ball circuits are formed in separate components, that is, the turnarounds are made in the end caps, one to each cap, while the return passages are constituted with the combined slider body and carriage housing. End seals to be kept in sliding contact with a tack rail are formed integrally with the carriage housing. Nevertheless, the linear guide means needs more than one fastener such as a bolt to join together all the slider body, end caps and carriage housing into an unit. As the turnarounds and the return passages provided for the recirculating-ball circuits are formed in separate components, that is, the turnarounds are made in the end caps, while the return passages are formed between the slider body and the carriage housing, accurate alignment in position of the turnarounds with the associated return passages is inevitable to ensure the recirculating-ball circuits allowing the rolling elements to run smoothly through there. Besides, the end caps and the carriage housing are made of the same synthetic resins.
In Japanese Patent No. 2846050 there is disclosed a linear sliding-motion bearing system having a slider that is comprised of a block of a thick plate provided underneath with a pair of widthwise opposing legs, an annular frame formed in a tetragonal configuration in top plan view so as to fit over the legs and having therein non-loaded raceway grooves allowing rolling elements to run through there with less subject to load, and a pair of elongated plates made therein with non-loaded raceway grooves, one to each plate. On assembly to complete the slider unit, the annular frame is secured around the legs by locking projections of the annular frame in recesses made on the outside faces of the legs. Then, the paired elongated plates are each fastened to the annular frame by inserting pins at four corners of the annular frame into holes in the elongated plates. With the linear sliding-motion bearing system constructed as stated earlier, since the annular frame is secured to the legs in a way the projections of the annular frame click into the associated recesses formed on the outside faces of the legs, there is no need to use any fastener such as a bolt or the like. Besides, the end seals are constructed to fit snugly in grooves formed in both the annular frame and the paired elongated plates. The linear sliding-motion bearing system recited above, though so constructed as to use no fastener such as a bolt in the assembly process, is adversely bulky in size because of the legs jutting out from the underneath of the thick plate. The non-loaded raceways provided between the confronting annular frame and elongated plates result in rendering the slider large in widthwise dimension. Any attempt to reduce the slider in width will result in rendering the legs slim in their breadth, thus raising a major disadvantage of reducing the slider in rigidity or stiffness. Besides, the recesses in which projections of the annular frame fit to join together them are formed in inner corners near the roots of the legs, while the annular frame is made considerably thick. This construction will plague the workers with a troublesome exertion of bending forcibly the projections to bring them into interlocking engagement with the inner recesses.
Another linear guide arrangement is disclosed in Japanese Patent laid-Open No. 248018/1992, in which a sliding block is composed of first and second block members, which are fastened together by screws.
In Japanese Patent No. 2775129 there is disclosed a linear guide arrangement in which a slider is constituted with a first member made therein with non-loaded passages for recirculating-ball circuits, a second member made with load raceway grooves, and third members arranged on forward and aft ends of the second member, one to each end, in a manner fitting in the first member together with the second member. With the linear guide arrangement recited just above, the first member is provided therein with the non-loaded area: return passages and turnarounds for the recirculating-ball circuits, whereas the second member is grooved to provide the load raceways. Thus, these members are made with drilled or cored holes in which fasteners fit to join together the members to complete the circulating-ball circuits.
The present invention, therefore, has as its primary object to overcome the problems as stated earlier and particularly to provide a linear motion guide arrangement adapted for use in machinery as diverse as semiconductor manufacturing machines, assembly machines and so on, which are made in a wide range of size. The present invention is more particular envisaged to provide a linear motion guide unit that is most preferable for use in very small machines. To this end, the linear motion guide unit of the present invention includes a slider constructed with a carriage, end caps and a carriage frame, each of which has any engaging means that may come into mutually fitting relation with a complementary engaging means of any counterpart, thus allowing to complete a composite construction with even either no use of fasteners such as bolts, screws and so on or no provision of deep recess for engagement with any projection. With the slider constructed as recited earlier, the carriage frame and the carriage, when being fit mutually, may be kept in accurate alignment in position with each other by the use of any positioning means between the carriage and the end caps. This contributes to making the slider as small as possible in size, with even inexpensive, and also reducing the number of parts or components required. No need of fasteners such as bolts and screws results in a reduction in manufacturing steps, with making the manufacturing process and assembly of parts easier, and further helping ensure the rigidity of the slider enough to realize smooth sliding motion of the slider along the track rail.
The present invention is concerned with a linear motion guide unit; comprising a track rail having first raceway grooves on lengthwise sides thereof, a slider conforming to the track rail to fit over the track rail for movement relatively to the track rail and also having second raceway grooves confronting the first raceway grooves, and a recirculating-ball circuit allowing rolling elements to run through there, the recirculating-ball circuit including a load raceway defined between the first and second raceway grooves, a turnaround formed in the slider and connected at any one end thereof with the load raceway, and a return passage formed in the slider and connected to another end of the turnaround; wherein the slider is composed of a carriage having the second raceway grooves on inside surfaces thereof and also having recesses and return-passage grooves on outside surfaces thereof, end caps arranged on fore-and-aft ends of the carriage, one to each end, and each made therein with the turnaround, and a carriage frame constituted with side panels facing the outside surfaces of the carriage and end panels facing fore-and-aft outside end surfaces of the end caps; and wherein the side panels of the carriage frame are each made on inside surface thereof with a projection to fit in the associated recess of the carriage, so that the carriage is accommodated together with the end caps into the carriage frame in such a manner that the projection of the carriage frame fits in the recess of the carriage to hold the carriage, end caps and carriage frame in an unitary composite construction.
In one aspect of the present invention, a linear motion guide unit is disclosed in which the carriage frame has a bottom plate covering underneath lower surfaces of the carriage and the end caps.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the side panels of the carriage frame are provided therein with recesses in which sides of the carriage are allowed to fit.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the turnarounds are each composed of a radially outside curved groove formed in the end cap, and a radially inside curved groove formed on a lug attached to a spacer, which is interposed between the carriage and any one of the end caps, with extending breadthwise between the side panels of the carriage frame. As an alternative, the lug is attached to the bottom plate of the carriage frame.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the return passage is composed of an inside raceway groove formed on the carriage, and an outside raceway groove formed in a tongue extending from the end cap in opposition to the inside raceway groove on the carriage. As an alternative, the carriage frame has an extension member on which is formed a raceway groove to be communicated with the raceway grooves of the end caps arranged on the fore-and-aft end surfaces of the carriage. In a further another aspect of the present invention, a linear motion guide unit is disclosed in which the bottom plate of the carriage frame is made therein with a hole, which is allowed to come into engagement with a projection that is formed underneath the tongue extended from the end cap.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the end cap has positioning pins to be fit into ends of the recesses formed on the carriage.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the projections formed on the carriage frame are provided at more than one location along lengthwise of the side panel.
In another aspect of the present invention, a linear motion guide unit in which the carriage frame has mounted with end seals, which are installed between the fore-and-aft end surfaces of the end caps and the inside surfaces of the end panels of the carriage frame. Moreover, the end seals fit in recesses, one to each recess, which are formed on the inside surfaces of the end panels of the carriage frame. In a further another aspect of the present invention a linear motion guide unit disclosed in which the end caps are each made on the outside end surface thereof with an overhang to fit in the recess on the inside surface of the associated end panel.
In another aspect of the present invention, a linear motion guide unit is disclosed in which all of the carriage frame, the end caps and the carriage are made with concaves conforming to the track rail, thus allowing the slider to fit over the track rail.
In another aspect of the present invention, a linear motion guide unit is disclosed in which there is provided a retainer band to keep the rolling elements in the carriage, with fitting in grooves formed on the end caps.
With the linear motion guide unit constructed as stated earlier, all of the carriage, the end caps and the carriage frame will be assembled mutually into a unitary composite construction ensured in desired rigidity or stiffness, rather than using any fastener such as bolts, screws and so on, by only press-fitting the projections of the carriage frame in the recesses of the carriage. The positioning means between the carriage and the end caps helps ensure the accurate position control among the components. Moreover, the lugs arranged on either the spacer or the carriage frame have advantages of providing the highly accurate turnaround in conjunction with the end caps, and further making the working process of the turnaround easier.
In the linear motion guide unit of the present invention, the slider moving along the track rail is constituted with only two components of the carriage and the composite of the carriage frame with the end caps, which are assembled into a united construction by mutual engagement of a fitting element with any complementary element, with no use of fasteners such as bolts and the like. This realizes reducing the number of components or parts, thus making the slider itself as small as possible. Thus, the present invention provides a linear motion guide unit that is applicable to machines diverse in type and size and most preferable for use in very small machines, with even requiring high precision.